Passive dosing dispensers of various geometries are disclosed in prior art patents. For instance, U.S. Pat. No. 650,161 which issued to J. Williams et al. on May 22, 1900 and U.S. Pat. No. 1,175,032 which issued to E. R. Williams on Mar. 14, 1916 disclose passive dispensers which are alternately flooded and then syphoned to a predetermined level. Also, U.S. Pat. No. 3,772,715 which issued to L. V. Nigro on Nov. 20, 1973, and U.S. Pat. No. 3,781,926 which issued to J. Levey on Jan. 1, 1974, and U.S. Pat. No. 3,943,582 which issued to J. Daeninckx et al. on Mar. 16, 1976 disclose passive dispensers which are alternately flooded and then gravitationally drained. Moreover, U.S. Pat. No. 3,407,412 which issued to C. T. Spear on Oct. 29, 1968, and U.S. Pat. No. 3,444,566 which issued to C. T. Spear on May 20, 1969 disclose dispensers which, although they have no moving parts, must be connected to a pressurized water supply such as the trap refill tube in a toilet tank and in which the direction of flow alternates in labyrinth passages.
Passive dosing dispensers of the type disclosed in the commonly assigned patent application of Robert S. Dirksing entitled PASSIVE DOSING DISPENSER EMPLOYING TRAPPED AIR BUBBLE TO PROVIDE AIR-LOCK, Ser. No. 002,524, filed Jan. 11, 1979, which is hereby incorporated herein by reference, have solved many of the problems associated with the aforementioned prior art dispensers, most particularly the problem of providing solid product and liquid product solution isolation from surrounding toilet tank water during quiescent periods. Dispenser embodiments of the type generally disclosed in FIGS. 1 and 15-18 of the aforesaid patent application of Robert S. Dirksing have been found particularly suitable for dispensing liquid solutions formed from solid products containing a surfactant. However, when the solid product exhibits a substantial tendency to form a hydrated gel while undergoing dissolution, even dispensers of the type disclosed in FIGS. 1 and 15-18 of the aforementioned patent application of Robert S. Dirksing may function with less than complete reliability due to the presence of excessive quantities of the incompletely dissolved gel within the dispenser.